1. Field of the Invention
The present invention relates to an internet phone system and a control method therefor, and in particular to an internet phone system which can remove a time delay of an internet phone itself by directly inputting an internet protocol IP address of the other party and by connecting the internet phone to a network without using a server, and a control method therefor.
2. Description of the Background Art
Recently, a local area network (hereinafter, referred to as xe2x80x9cLANxe2x80x9d) has been used as a more important communication means than a telephone network in offices. However, the LAN and the telephone network (extension telephones) are individually formed, thus requiring a double cost.
Accordingly, in order to solve the above-mentioned problem, the telephone network is replaced by the LAN by employing a terminal which can be operated in the LAN (hereinafter, referred to as xe2x80x9cIP phonexe2x80x9d).
FIG. 1 is a constitutional diagram illustrating a state where a protocol based on a conventional call server is applied to the IP phone. As shown therein, a plurality of IP phones) IP Phone 1xcx9cIP Phone N and a plurality of personal computers PC 1xcx9cPC N are connected to the LAN. In addition, a call server having all state information and intermediating between the IP phones is connected to the LAN.
The link establishment process of the conventional IP phone will now be explained with reference to the accompanying drawings.
FIG. 2 is a state view illustrating the link establishment process of the conventional IP phone. As shown therein, a call step for link establishment starts hen the first IP phone IP Phone 1 outputs a setup message to the call server.
The call server checks a state of the first IP phone IP Phone 1 and a state of the second IP Phone 2 to which the first IP phone IP Phone 1 intends to link, and judges whether a link can be established therebetween. As a result of judgement, if the second IP phone IP Phone 2 can be linked, the call server outputs the setup message to the second IP phone IP Phone 2.
Thereafter, the second IP phone IP Phone 2 receiving the setup message confirms that it can be linked, and outputs a connect message to the call server. The call server outputs the connect message to the first IP phone IP Phone 1, thereby establishing the link between the first and second IP phones IP Phone 1, IP Phone 2.
FIG. 3 is a call processing flowchart of the conventional IP phone showing the process as shown in FIG. 2 in more detail.
Firstly, when dialing (S1), the setup message is transmitted to the call server (S2). Whether a state of the terminal at the designation is idle is judged (S3). If not, a setup rejection message is transmitted to a source IP phone (S4). If it is idle, the setup message is transmitted to a designation IP phone (S5), and whether the setup is accepted is judged (S6). If not, the setup rejection message is transmitted to the call server (S7), and to the source IP phone (S9), thereby disconnecting the call. When the setup is accepted in step 6 (S6), the connect message is transmitted to the call server (S8), and to the source IP phone (S10), thereby connecting the call and starting a bidirectional voice transmission.
In the case that the personal computers are used in the conventional art as described above, a voice delay time is generated due to a limit of the operating system OS, in addition to the network delay time. Accordingly, a real time voice communication cannot be performed, thus reducing reliability of communication quality. When the IP phones are employed in order to overcome such a disadvantage, an operation cannot be carried out without a server. As a result, it is necessary to install the server merely for the operation of one internet phone, which results in complicated works and increased costs.
Accordingly, it is an object of the present invention to provide an internet phone system which can remove a time delay of an internet phone itself by directly inputting an internet protocol IP address of the other party and by connecting the internet phone to a network without using a server, and a control method therefor.
In order to achieve the above-described object of the present invention, there is provided an internet phone system including: an Ethernet controller processing a medium access control frame received from a LAN; a switch unit selecting one of analog voice signals inputted from a speaker or handset in accordance with a control signal; a codec processing the analog voice signal inputted from the switch unit or a signal inputted from the LAN; a key input unit processing a key button input; a memory unit storing an inputted data; and a central processing unit controlling the whole operation of the internet phone system.
In addition, an internet phone processing flow in accordance with the present invention includes: a first step of dialing; a second step of transmitting a setup message to a designation IP phone; a third step of discriminating whether a setup is accepted; a fourth step of transmitting a setup rejection message to a source IP phone and disconnecting a call, when the setup is not accepted in the third step; and a fifth step of transmitting a connect message to the source IP phone, connecting the call, and starting a bidirectional voice transmission, when the setup is accepted in the third step.
A more detailed control method for an internet phone system according to the present invention includes: a first step of judging whether a key button signal is inputted; a second step of judging whether a ring signal is inputted, when the key button signal is not inputted as a result of judgment in the first step. Next, a third step of processing the key button signal in accordance with H.323 and transmission control protocol/internet protocol TCP/IP occurs, and processing a medium access frame (call control frame), when inputted as a result of judgment in the first step occurs. Then, a fourth step of judging whether the other party responds occurs, when the third step is finished. Next, a fifth step of processing a voice signal in a codec, processing it in accordance with real time protocol/user datagram protocol/internet protocol RTP/UDP/IP, processing a medium access control frame (voice frame), and communicating with the other party, when the other party responds as a result of judgment in the fourth step occurs. Then, a sixth step of performing the fifth step, when the ring signal is inputted as a result of judgment in the second step, or returning to the first step when the ring signal is not inputted occurs. Finally, a seventh step of transmitting a busy signal and finishing the process occurs, when the other party does not respond as a result of judgment in the fourth step.